Clutch control mechanism



SePt- 25, 1951 E. E. HUPP CLUTCH CONTROL MECHANISM 2 Sheets-Sheet 1 Filed Aug. 27, 1945 INVENTOR.

ATTORNEY Sept. 25, 1951 E E, HUPP 2,569,003

CLUTCH CONTROL MECHANISM Filed Aug. 27, 1945 2 Sheets-Sheet 2 77 :F1 EE INVENTOR. f/wfI//a Patented Sept. 25, 1951 zssaoo cLU'rcn coN'rnoi. Meenemen Edward E. Hup, South Bend, 1nd., assigner to Bendix Aviation Corporation, South Bend, Ind., a lcorporation of Delaware Application August 27, 1945, Serial No. 612,812

e claims. 1

This invention relates in general to clutch control mechanism and in particular to a pressure differential operated clutch control mechanism for operating the friction clutch of an automotive vehicle.

It is an object of my invention to provide power means for operating the friction clutch of an automotive vehicle said power means including a pressure differential operated motor controlled by an operation of the accelerator of the vehicle. the shift lever of the vehicle, a vehicle speed responsive governor and means operable in accordance with the speed of the engine of the vehicle.

When the friction clutch of an automotive vehicle is operated by a power means it is of course desirable that said power means simulate as closely as possible a skillful manual operation of the clutch. It istherefor the most important object of my invention to provide a clutch operated pressure dierential operated motor. the power element of which is so controlled that in effecting the clutch engaging operation of the said motor the load of said clutch plates is directly proportional to the R. P. M. of the internal combustion engine of the vehicle; for by this operation there is, under all conditions of clutch operation, sumcient force developed by the engine to drive the driving plate of the clutch.

Yet another object of my invention is to provide a two stage pressure diierential operated motor for operating the Afriction clutch of an automotive vehicle, the clutch disengaging operation of said motor being in large measure controlled by an operation of a three way valve controlled by an operation of the accelerator, a vehicle speed responsive governor and the transmission controlling shift lever .of the vehicle; and the clutch engaging operation of said motor being in large measure controlled by an air bleed operation of said three-wayivaflve said operation being controlled by an operation of the accelerator, the generator of the vehicle or other engine speed responsive mechanism, and a governor controlled vacuum cut-in valve.

A further object of my invention is to provide power means for operating the friction clutch of an automotive vehicle said power means including a single-acting pressure diiferential operated motor controlled by an accelerator, a gear 4shift lever and a governor controlled three-way valve operable to effect a clutch disengaging operation of said motor and to initiate the first stage of a two-stage clutch engaging operation of said motor. the clutch plate contacting operation, that is. the second stage of operation of said motor, being controlled by a bleed valve operation of said three wayV valve and being operable to control the flow of air into said motor, said bleed valve operation being controlled by an engine speed responsive means and by a pressure differential operated motor operable in accordance-with the degree of gaseous pressure within the clutch operating motor.

A further object of my invention is to provide power means for operating the friction clutch of an automotive vehicle said power means including a single-acting pressure diilerential operated motor controlled by a power operated three-way valve said valve being operative with the release of the accelerator and with an operation-of the shift lever of the vehicle or a vehicle speed responsive governor to effect a clutch disengaging operation of the motor said valve being also operative, witha depression of the accelerator, an operation of either the governor or the shiit lever and an operation of an engine speed responsive electromagnet, to effect a clutch engaging operation of the motor the load of the clutch plates of the-clutch being directly proportional to the speed of the engine.

The most important object of my invention however is to provide a pressure differential operated motor for operating a friction clutch of an automotive vehicle said motor being controlled by a single valve unit said unit including an electrical means operative in conjunction with the operation of other electrical controls, to effect a clutch disengaging operation of the motor when the accelerator is released and either the shift lever of the car is moved to effect an operation of the transmission or the car is slowed down below a certain speed, said electrical means being also operative, in conjunction with an operation of the aforementioned controls, to eiect a second stage clutch engaging operation of the 'motor the loading of the clutch plates during this operation being directly proportional to the speed of the engine.

Yet another object of my invention is to provide power means for operating a standard friction clutch of an automotive vehicle said power means being controlled by an electrically controlled valve unit said valve unit comprising a pressure balanced three-way valve and a solenoid operated vacuum cut-0E valve.

A further object of my invention is to provide a single-acting pressure differential operated motor for moving the driven plate of the friction clutch to its clutch disengaged position and for ,seaoos controlling the operation of the clutch springs plate into engagement with the driving. clutch plate, the clutch engaging operation of said motor being controlled in part by a pressure balanced type oi follow-up valve said valve being controlled by an operation of the accelerator and the generator of the vehicle or other mechanism the operation of which' is directly proportional to the speed of the engine. t

Yet another and important object of my invention .is to provide a vacuum operated motor for operating the friction clutch of an automotive vehicle said motor being controlled by a single electromagnetically controlled compact valve unit.

Other objects of the invention are referred to in connection with the following detailed description of the accompanying drawings, which represents a preferred embodiment of the invention. After considering this example, skilled persons will understand that many variations may be made without departing from the principles disclosed; and I contemplate the employment of any structures, arrangements or modes of operation that are properly within the scope of the appended claims.

Figure 1 is a diagrammatic view disclosing the principal elements of the clutch control mechanism constituting my invention; and

Figure 2 is a sectional view of the control unit constituting the essence of my invention.

Describing now that embodiment of my invention disclosed in the several figures of the drawing the principal elements thereof consist of a single acting vacuum motor ||l comprising a casing |2 and a power element such as a piston, not shown, which is connected to a friction clutch, not shown, of a conventional design, that is, one including driving and driven elements. One end of the casing of the motor, a portion of the body thereof, and the power element together outline the control chamber, the gaseous pressure within said chamber being controlled to control the operation of the motor. The force transmitting means interconnecting the power element of the motor with the clutch preferably includes a flexible cable i6 connected to a crank i6; and said crank is flxedly connected to a shaft i6 which is connected to the clutch. A foot operated clutch pedal 20, contactable with a stop 2| extending from the crank I6, is also preferably included in the clutch operating mechanism.

One end of the motor l0. that is the end of the same constituting a part of the aforementioned power compartment, is connected by a conduit 22 to an outlet port 26 of a control valve unit 26.

This unit, constituting the most important feature of my invention, includes a three way valve, means for actuating said valve. a vacuum cut-off valve and means for actuating said cut-off valve. The entire control valve mechanism of my invention is built into this simple compact unit 26 and the parts of the same are so constructed and arranged that the valve may be easily serviced.

Describing now the details of the control valve unit 26 the same include two hollow casing members 26 and 30 secured together by fastenings 32 which fastenings also serve to clamp a diaphragm 66 in place between said casing members. It follows therefore that by virtue of the diaphragm there are provided two valve compartments said compartments being indicated by the reference numerals 36 and 66. To the central portion of the diaphragm there are secured armatures 46 and 42 of electromagnets 44 and 46 respectively. The

former electromagnet is housed within the compartment Il and is secured to the casing member I0 by a fastening 66. The winding 66 of the electromagnet 46 is wired to terminals 62 and 66 mounted in the casing member 26 and the winding 66 of the electromagnet 66 is wired to terminals 66 and 66 mounted in the casing member l0. To the armature 60 there is threadediy secured a pin 62 and said pin extends within and is secured at 66 to one end of a hollow spool shaped three-way valve member 66. This valve is slidably mounted withina sleeve member 66 which is preferably flxedly mounted within one end of the valve casing member 60. The latter member is provided with a duct 1l leading to a casing projection 12 which is recessed at 14 to house a vacuum cut-off valve member 16. This valve member is moved upwardly and downwardly respectively by a spring 11 and the armature 16 of a solenoid 60 said movement serving to cover or uncover a port 62; and to this port there is secured a conduit 64 leading to the intake manifold 66 of the internal combustion engine 66 of the vehicle. A vacuum tank 66 may be included in this fluid transmitting connection between the manifold and cut-oi! valve 16 and the evacuation of said tank is insured by the inclusion of a check valve 62 incorporated in said connection.

Completing the description of the principal fea` tures of the valve unit 26 the armature I2 is biased downwardly, Figure 2, by a spring 64 said spring being interposed between one end of said armature and one end of a screw 66 which is adjustably mounted in a fitting 60 secured to the casing member 26.

Describing now the electrical control means of my invention as is disclosed in Figure 1 the electromagnet 60, which together with the spring 11 operates the vacuum cut-oi! valve 16, is controlled by grounded selector lever operated switches 66 and |00 and by a grounded vehicle speed responsive governer operating switch |02; and the winding 66 of the electromagnet M, operative to actuate the valve member 66, is controlled by the aforementioned switches 66, |66 and |02 and by an accelerator operated switch |04. The construction of the latter switch and its connection with the accelerator |06 is such that the same is closed when the accelerator is completely released and is opened prior to taking up the lost motion of a lost motion connection |66. A transmission and clutch operating selector lever |08 is connected with the switches 66 and |00 and with the transmission operating cranks ||6 and ||2, by the force transmitting links and levers disclosed in Figure 1. The construction of these connections is described in detail hereinafter.

As to the electrical means for controlling the electromagnet 46 as is disclosed in Figure 1 said electromagnet is preferably wired to a source of electrical current for example the generator ||6 whereby the degree of energization of said electromagnet, that ls the degree of current flowing through the winding 56, is directly proportional to the R. P. M. of the internal combustion engine of the vehicle. A voltage regulator |6l wired to the battery lil and to the electromagnet I6 may be included in the electrical hookup. It is to be particularly noted however that the current ilow through the electromagnet 46 need not necessarily be controlled by the generator III of the car; for it is within the purview of my invention to employ any engine driven mechanism as a means for controlling the current sent through the winding 60 it being absolutely ,necessary however that the degree of said current be directly proportional to the speed of the engine.

Describing now in detail the aforementioned shift lever operated force transmitting means for actuating the switches 98 and |00 and the transmission operating cranks and H2, a spring |20, interposed between a stop |22 iixedly secured to the steering post |24 of the vehicle and a stop |26 iixedly secured to a shaft |20. serves to bias said shaft downwardly to the position disclosed in Figure 1. Now to the lower end of the shaft |28 there is fixedly secured a crank |30 through which extends a pin |32; and when said shaft is moved downwardly by the spring |20 one end of said pin extends within a slot |34 within a floating crank |36. To one end of the crank |34 there is pivotally connected a rod |40 said rod being pivotally connected to one end of the crank ||2. This crank when rotated clockwise serves to actuate the other force transmitting v means Within the casing of a three speeds forward and reverse transmission |42 to establish the transmission in its high gear setting; when the crank |36Lis rotated counterclockwise said transmission is established in its second gear setting.

'I'he crank ||0 when rotated clockwise serves to establish the transmission |42 in its low gear setting and when rotated counterclockwise serves to establish said transmission in reverse gear. The connection between the crank ||0 and the shift lever |08 includes a link |44 pivotally connected to a floating lever |46 said lever being slidably mounted on the shaft |28. This lever |46 -is provided with a slot |48v to receive one end of the pin |32. l

When the driver wishes to establish the transmission in its second gear setting he rotates the shift lever |08 counterclockwise and this operation serves to rotate the floating lever |36. Now the switch 98 is preferably so constructed that the force necessary to close the same, that is, the force necessary to compress a spring within the switch connected to its movable contact, is less than the 'force necessary to effect the initial movement of the high, second shift rail of the transmission. It follows therefore that the initial movement of the shift lever results in a pivoting of the lever |36 about its connection with the link |40; and this operation results in a closing of the clutch controlling switch 88. Continued movement of the shift lever, that is, the movement after the switch 88 is closed and there is no possible further movement of a link |50 interconnecting the lever |36 with said switch, results in a pivoting of said lever about its pivotal connection with the link |50; and this operation results in the operation of the transmission to establish the same in its second gear setting. After this setting is established the driver removes his hand from the shift lever whereupon the aforementioned spring within the switch 98 operates to open said switch. This switch is so constructed that the same is also closed when the driver moves the shift lever to establish the transmission in its high gear setting; and the spring means within said switch also functions to openthe same when the high gear setting of the transmission has been established and the driver removes his hand from the shift lever.

Describing the operation of the switch mechanism to establish the transmission in either reverse gear or low gear the driverrst rotates the shift lever upwardly in a plane perpendicular to the plane of the steering wheel; and this operation serves to bodily move the shaft |20 upwardly against the tension of the spring |20. The upper end of the pin |32 is by this operation moved into the slot |48; and a'subsequent rotation of the shift lever, either to establish the transmission in reverse or low gear, results in a rotation of the cranks |30 and ||0 and the lever to effect one or the other of these settings of the transmission. The shaft |28 is provided with a recessed portion |52 which receives a pin |54 operably connected to the grounded switch |00; and as will be obvious from an inspection of Figure 1' when said shaft is moved upwardly, in the operation of establishing the transmission in either reverse gear or low gear, the switch |00 is closed by virtue of the forcing of the pin |54 to the left. Figure 1, when the end of said pin is forced out of the recess |52 and onto the full bodied portion of the shaft.

There is thus provided, by the above described shift lever operated switch mechanism, means for effecting a clutch disengaging operation of the motor |0 during the first increment of movement of the shift lever as it is moved to establish the transmission in one of its four gear settings. To effect this operation however it is of course necessary to first release the accelerator to close the switch |04. The parts of the mechanism are preferably so constructed and arranged that the clutch is disengaged before the transmission is operated. It is to be noted that the switch operating force transmitting means of my invention is such as to effect a closing of the switch mechanism when the shift lever is moved in either one of two different planes.

Briefly describing this clutch disengaging operation when the switch |04 and one or the other of the switches 98, |00 andA |02 is closed then the ground connection to the electromagnet 44 is completed; and as described in Figure 1, the hot wire from the said electromagnet includes a cutout switch |56, the ignition switch |58 of the electrical system of the car and the grounded battery-I I8.

With the closing of the latter circuit the electromagnet 44 is energized and with this operation the valve 66 is operated to effect a connection with the intake manifold thereby energizing the motor I0 to effect a disengagement of the clutch. The electrical circuit including the electromagnet is also closed with this operation thereby effecting an opening of the valve 'I6 to provide a source of vacuum.

Describing now the complete operation of the mechanism constituting my invention and incidentally completing the description of the parts thereof not heretofore described, when the accelerator |05 is released to close the engine thrcttle and thereby idle the internal combustion engine 88 the intake manifold 86 of said engine is partially evacuated and there is thus provided a source of vacuum for energizing the motor I0 to disengage the friction clutch of the automotive vehicle; and as described above this operation is effected with a release of the accelerator and either a gear shifting operation of the shift lever |08 or a lowering of the speed of the vehicle below governor speed to close the switch |02, either of said ,operations effecting an energization of the solenoid 44 to effect an opening of the valve 66. Now at this' juncture it is to be explained that so constructed and arranged and so operative that at this time the valve Il and means for operating the same assume the relative positions disclosed in Figure l. The small bodied portion of the valve It moves to place ports I and |62 in the sleeve I in communication with each other thereby interconnecting the vacuum tank Il with the control chamber of the motor il. Now at this time the diaphragm Il and the valve connected thereto are biased upwardly. Figure 2, by virtue of the differential of pressures to which the diaphragm is subiected; for the compartment 30 is at the time, by virtue of a connection with the motor Il, partially evacuated the gaseous pressure within said compartment being equal to that within the control chamber of said motor. This result is accomplished by means of a duct I, Figure 2, in the valve casing. Now the compartment 2l lof the control unit 2l is at the time vented to the atmosphere by a port Ill connected to an air cleaner I by` a conduit i1l, accordingly it follows that therdiaphragm 34 is loaded by the differential of pressures acting on the same to bias the same upwardly. The valve member is also at this time. that is, when the engine I8 is idling and the solenoid Il is energized to effect a disengagement of the clutch, biased downwardly, Figure 2, by the loading of the spring M and upwardly by the engine idling loading of the electromagnet It is apparent therefore that the resultant of the four loadings to which the valve member It is then subjected effects the above described valve open. that is, clutch disenlng position of the valve member Il.

Continuing the description of a cycle of operations of the clutch control mechanism of my invention, te initiate a clutch engaging operation of the motor Il the driver either depresses the accelerator to open the switch I as the lost motion connection lill is being taken up or removes his hand from the shift lever III after completing the operation of establishing the transmission in gear. This latter operation serves of course to open one or the other of the switches il and III depending upon which one had been closed by an operation of the shift lever. The solenoid M is, by either of these operations, deenergized resulting in an unbalancing of the aforementioned four loadings maintaining the valve I in its open position; and this operation results in an upward movement of said valve to vent the motor il to the atmosphere. 'Ihere is then a ilow of air into the motor III via the air cleaner I, conduit I1l, port ill, chamber 32. the interior of the valve member OI, a port i12 in said member. ports I" and 24 and the conduit 22. The clutch springs then function to move the driven clutch plate toward the driving clutch plate and the parts of the mechanism are so constructed and arranged that when the gaseous pressure within the control chamber of motor il reaches a certain factor said movement is arrested by the lapping of the valve member this operation preferably taking place when the clutch plates contact lightly, that is, with a load insufficient to either stall the engine or effect a movement of the car from a position of rest. Describing this clutch engaging operation of the mechanism in other words, the

summation of the idling engine loading of the electromagnet plus the loading effected by the diaphragm I4 minus the loading effected by the spring Il is such as to nrst effect an upward movement of the valve member to vent the motor to the atmosphere to initiate the above described iirst stage of clutch engaging operation;

and when the gaseous pressure within the oompartment 3l reaches a certain factor then said valve member automatically moves downwardly to lap the three-way valve member 0l. In effecting this operation it is to be remembered that the gaseous pressures within the moter ill and the compartment 38 are the same at all times. In this lapped position ofthe valve member a la'xd portion |14 of said member covers the port To edectively engage the clutch, that is, bring the clutch plates into driving contact with each other the driver then depresses the accelerator to open the throttle thereby increasing the speed of the engine above its idling speed; and this operation upsets the above described valve lapping equilibrium of forces by increasing the loading on the valve member tl from the electromagnet 46. It follows therefore that the valve member 66 is again moved upwardly to vent the motor ill and compartment 20 to the atmosphere; and as a result of this operation when the gaseous pressure within said compartment is increased suiilciently to oiiset the increase in loading from the electromagnet 46 then the valve is again lapped. It follows therefore that the summation of the three forces acting to lap the valve is a constant. It will be apparent therefore that subsequent increases in the speed of the engine results in an increase in the clutch plate loading said loading being at all times directly proportional to the engine speed.

It is apparent therefore that with the clutch control mechanism of my invention there is provided means for effecting a disengagement of the clutch whenever the accelerator is released sumciently to close the switch i and when either the car is travelling below governor speed or the gear shift lever i" is operated to shift gears in the transmission. To engage the clutch the driver depresses the accelerator to open the switch IM or removes his hand from the shift lever after completing an operation of the transmission said latter operation effecting an opening of either one or the other of the switches Il and |00; and this operation results in a first stage of engagement of the clutch. The second stage of engagement of the clutch, in which the degree of loading oi' the clutch plates is directly proportional to the speed of the engine. is effected by an opening of the throttle.

Describing the operation of the vacuum cut-oi! valve 16 it is to be noted that with this valve incorporated in the mechanism the clutch may be disengaged when and only when either the car is travelling below governor speed or the gear shift lever is operated to operate the transmission; for then said valve 16 is open to provide a source of vacuum to make possible an energization of the motor i0. Above governor speed, that is, when the vehicle speed is such that the electromagnet Il is deenergized, the cluteh control motor is inoperative to disengagey the clutch; for said motor is then vented te the atmosphere via ports ill and |82 in the casing housing the electromagnet Il and the other connections with the motnr Il disclosed in Figure 2. Now below governor speed it is desirable to maintain the valve member lt in communication with the source of vacuum, that is, the tank lil; for if during the operation of engazing the clutch the engine speed, due to say an engine laboring operation, is unduly slowed down then it is desirable to at once decrease the clutch plate loading which causes this undesirable operation of the engine. This operation will be efi'ected with the mechanism of my invention inasmuch as the valve member 66 will then momentarily reconnect the clutch motor with the vacuum tank.

It is thought that the invention and many of its .10 clutch of an automotive vehicle comprising a pressure differential operated motor, and valve means for controlling the operation of said vmotor. including a hollow casing ported to proattendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advanttages, the forms hereinbefore described being merely a preferred embodiment.

I claim:

1. In an automotive vehicle provided with a friction clutch, power means for operating said clutch to effect a disengagement of the clutch and a controlled engagement thereof said power means comprising a pressure differential operated motor the power element of which is operably connected to the clutch, and valve means for controlling the operation of said motor including a hollow casing ported to provide an atmospheric vent opening, a port to be connected to the aforementioned motor, a port to be connected with a source of vacuum, a reciprocable three-way valve member housed within said casing said member being movable to one position to interconnect the two aforementioned ports and to another position to interconnect the iirst mentioned port with the atmospheric vent opening, and means, within said casing, for actuating said reciprocable valve member to control the operation of the valve means, said valve actuating means including a solenoid operable, when energized, to move the valve member to the i-lrst of the aforementioned two positions, said means further including an electromagnet, a spring and a pressure differential operated diaphragm for controlling the movement of the valve member to a position to vent the motor to the atmosphere and to then lap said member to thereby cut off the flow of air to or from the motor.

2. In an automotive vehicle provided with a friction clutch, an internal combustion engine, a gear shift lever, a vehicle speed responsive governor, an accelerator, a throttle, and means, including a lost motion connection, interconnecting the accelerator and throttle; power means for operating said clutch to effect a disengagement of the clutch and a two-stage engagement thereof, said power means comprising a pressure differential operated motor the power element of which is operably connected to the clutch, and valve means for controlling the operation of said motor, including, as a single unit, a hollow casing, a reciprocable three-way valve member housed within said casing, means within the casing for actuating said valve member comprising an electromagnet operable, when energized, to effect a clutch disengaging operation of the motor and further comprising an electromagnet, a spring and a pressure differential operated diaphragm operable to effect a controlled clutch engagingy operation of the valve member, together with electrical means for controlling the operation of said electromagnets including an accelerator operated switch opened during the taking up of the aforementioned lost motion connection and further including shift lever operated switch mechanism and a governor operated switch, the latter switches and switch mechanism serving to control the operation of the rst mentioned electromagnet.

3. Power means adapted to operate the friction vide an atmospheric vent opening, a port to be connected to the aforementioned motor, a port to be connected with a source of vacuum, a reciprocable three-way valve member housed within said casing, said member being movable to one position to interconnect the two aforementioned ports and to another position to interconnect the first mentioned port with the atmospheric vent opening, and means. within said casing, for actuating said reciprocable valve member to control the operation of the valve means, said valve actuating means including an electromagnet and a pressure differential operated power element operative to move the valve member in one direction and further including an electromagnet and a spring operative to move the valve member in the opposite direction.

4. Power means for operating the friction clutch of an automotive vehicle including a pressure diierential operated motor operably connected to the clutch, valve means for controlling the operationoi said motor including a valve casing having a ,vacuum port adapted to be connected to a source of vacuum, an atmospheric port'and a port adapted to be connected to said motor, a reciprocable pressure balanced valve member within said casing operable in one of its positions to interconnect the vacuum port with the port connected to the motor and operable in another of its positions to interconnect the atmospheric port with the port connected to the motor, means within the valve casing for actuating the valve member including four separate loading elements, the operation of said four elements serving to move the valve member to control the operation of the clutch operating motor, and means for controlling the operation of said loading elements.

5. Power means for operating the friction clutch of an automotive vehicle including a pressure differential operated motor operably connected to the clutch, valve means for controlling the operation oi said motor including a valve casing having a vacuum port adapted to be connected to a source of vacuum, an atmospheric port and a port adapted to be connected to said motor, a reciprocable valve member within said casing operable in one of its positions to interconnect the vacuum port with the port connected to the motor and operable in another of its positions to interconnect the atomspheric port with the port connected to the motor, means within the valve casing for actuating the valve member including two separate electromagnetic means, a pressure differential operated diaphragm, and a spring, and means for controlling the operation of said electromagnetic means, diaphragm and spring.

6. Power means for operating the friction clutch of an automotive vehicle including a pressure differential operated motor operably connected to the clutch, valve means for controlling the operation of said motor including a valve casing having a vacuum port adapted to be connected to a source of vacuum, an atmospheric port and a port adapted to be connected to said motor, a reciprocable valve member within said casing operable in one of its positionsto interconnect the vacuum port with the port connected to the motor and operable in another of its positions to interconnect the atmospheric port with the port connected to the motor, means within the valve casing for actuating the valve member including two separate electromagnetic means, a pressurediilerential operated diaphragm, and a spring,

and means for controlling the operation of said 5 vvelectromagnetic means, diaphragm and spring,

@WARD E. HUP?.

12 nmmlczs crrnn The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Nam'e Date 2.049.739 H111 et ll. A118. 4, 1936 2,317,216 Paton Apr.v 20, 1943 A 2,326,943 H111 Allg. 17, 1943 2,395,469 Hey et a1. Dec. 19, 1944 2,391,192 Price Dec. 18; 1945 

